This invention relates to a method of producing surfactants from lignin and to a method of recovering oil from subterranean formations with surfactant flooding systems that incorporate lignin surfactants.
Surface active compounds or surfactants have become extremely important chemicals in our society. Numberless types of surfactants are used for a myriad of applications. To work effectively, surfactants require water soluble and oil soluble characteristics. It is these mixed characteristics which enable surfactants to lower the interfacial tension between two disparate liquids.
One problem with many surfactants is their high cost of manufacture. Surfactants which are relatively cheap have an inherent advantage in the market place.
A minor use of surfactants has been in surfactant flooding systems for enhanced oil recovery. But because of the relatively high cost of surfactants, surfactant flooding systems for oil recovery have generally not been economical. The economics of surfactant flooding have additionally become more unfavorable recently with the low price of oil.
Surfactant flooding to recover oil has been actively investigated due to the relatively poor ability of water floods to displace remaining oil from a reservoir's pore structure. Because of the structure of the reservoir and relative interfacial tensions involved, the flood water may form channels or fingers, bypassing the oil in the formation. Even where water has flowed, residual oil is trapped in pores by viscous and capillary forces. Further flooding with water will not remove such oil.
Investigations of ways to increase oil recovery by improving the displacement ability of water floods have produced useful surfactants which reduce the interfacial tension between oil and water in the reservoir. With lower interfacial tensions, oil that is trapped in the pore structure can be dispersed into the water as smaller and more easily deformable droplets. Many types of surfactants have been investigated and the choice of which surfactant to employ in a water flood operation is dependent upon reservoir characteristics as well as the cost and availability of the surfactants.
Most surfactant floods have employed a petroleum sulfonate as a sole surfactant, or at least a major component of a mixture of surfactants. Synthetic alkyl benzene sulfonates and alkyl sulfonates and sulfates have also been proposed as oil recovery surfactants. To combat separation problems in surfactant mixtures, especially at high salinities (&gt;2% salt), a material with both water soluble and oil soluble characteristics is usually added to sulfonate surfactant mixtures. These materials are generally referred to as "solubilizers" and are usually sulfate or sulfonate salts of polyethoxylated alcohols or alkylphenols. The choice and concentration of solubilizer employed is dependent upon the choice of surfactants used, their overall concentration, and salinity.
The reduction of lignins to produce certain simpler compounds is known in the art. The transformation of lignins to commodity chemicals such as benzene, phenol or cresol by hydrogenation has been extensively researched. Carbon monoxide reduction is a little known area. Some work has been done on the reduction of coal by carbon monoxide, but little investigation has been made into the reduction of lignins by carbon monoxide.
The extensive research into the hydrogenation of lignins generally fits into two categories. Studies have been concerned with either the hydrogenation of wood as a pulping method or with the hydrogenation of lignin as a method to produce commodity chemicals. In the 1960s, Crown Zellerbach extensively studied the Noguchi process for converting desulfonated lignins to monophenols by catalytic hydrogenation. This is discussed in Goheen, D. W., "Hydrogenation of Lignin by Noguchi Process", Lignin Structure and Reactions, R. F. Gould, ed., ACS (1966).
More recently, Hydrocarbon Research, Inc. developed the Lignol process for converting kraft lignin to benzene and phenol as discussed in U.S. Pat. No. 4,420,644, and Huibers, D. T. A. and Jones, M. W., Can. J. Chem. Eng., Vol. 58, p. 718-722 (1980). This process achieved 20% to 35% yields of distillable monophenols. The Lignol process was designed to produce saleable commodity chemicals by adding separation and purification steps to the hydrogenation process.
Continental Can Company has published results of their research on aqueous hydrogenation of kraft lignin involving catalysts such as Raney Nickel and Raney Copper. Please see, Benigni, J. D., and Goldstein, I. S., J. Polymer Science. Part C, p. 467-75, 477-78 (1971).
The Noguchi, HRI, Lignol, and Continental Can processes used non-sulfonated lignin to keep from poisoning the hydrogenation catalyst with sulfur. This restriction placed a further limitation on the hydrogenation reaction as non-sulfonated lignins are less readily available than lignin sulfonates. Therefore, research was directed to hydrogenating lignin sulfonates with sulfur resistant catalysts. Generally, these processes have used an iron catalyst in a pasting oil that consists of the high boiling residue from the previous hydrogenation. These processes which yield 30% to 60% conversion of lignin sulfonate to distillable products are described in U.S. Pat. No. 3,253,044 and Canadian patent No. 559,006.
The hydrogenation of wood has also been studied to determine the types of compounds produced. Please see, Boocock, D. G. B., Mackay, D., McPherson, M., Nadeau, S., and Thurier, R., Can. J. Chem. Eng., Vol. 57, p. 98-101 (1979); Boocock, D. G. B. and Mackay, D., Energy Biomass Wastes, Vol. 4, p. 765-77 (1980); Boocock, D. G. B., Kallury, R. K. M. R., and Tidwell, T. T., Anal. Chem., Vol. 55 p. 1689-94 (1983); Bhaskaran, T. A. and Schuerch, C., Tappi, Vol. 52, p. 1948-52 (1969); and Burton, A., DeZutter, D., Grange, P., Poncelet, G., and Delmon, B., Comm. Eur. Commun., p. 935-9 (1983).
Two references have been found in the coal literature which imply that carbon monoxide and water may be better reducing agents for lignins than hydrogen. Please see, El-Saied, H. and Oelert, H. H., "Liquefaction of the Lignohemicellulosic Waste from Sulphite Spent Liquor," Cellulose Chem. Technol., Vol. 14, p. 507-516 (1980); and Baltisberger, R. J., Stenberg, V. I., Klabunde, K. J., and Woolsey, N. F., "Chemistry of Lignite Liquefaction," Final Progress Report January 1980 - December 1982, DOE/FC/02101-23, July 1983, p. 68-71 and 97-110. The DOE report cited above also discloses that sulfur-containing materials could act as catalysts in carbon monoxide reductions of coal. Finally, a reference entitled "Dissimilar Behavior of Carbon Monoxide Plus Water and of Hydrogen in Hydrogenation," by Herbert Appell, Irving Wender and Ronald Miller of the Pittsburgh Coal Research Center of the U.S. Bureau of Mines published in American Chemical Society, Div. Fuel Chem., Prepr., Vol. 13(4), p. 39-44, reports one laboratory run where a small quantity of lignin was reduced by carbon monoxide to yield a benzene soluble material.